1. Field of the Invention
The present invention relates to an electrophotographic photoconductor and a process cartridge and an electrophotographic apparatus having the electrophotographic photoconductor.
2. Description of the Related Art
As an electrophotographic photoconductor for use in an electrophotographic apparatus, an electrophotographic photoconductor having an undercoat layer containing metal oxide particles and a photosensitive layer containing a charge generation material and a charge transport material formed immediately on the undercoat layer is used.
As the metal oxide particles for use in the undercoat layer, tin oxide particles, titanium oxide particles, zinc oxide particles, and the like are used. Among the above, it is known that the electrical resistance of the tin oxide particles varies depending on the oxygen deficiency degree and the electrical resistance of the tin oxide particles becomes lower with an increase in the oxygen deficiency degree.
However, in the undercoat layer containing the tin oxide particles, moisture and the like in the atmosphere are likely to adhere to the surface of the tin oxide particles, so that the oxygen deficiency is inactivated, which increases the electrical resistance of the tin oxide particles, and thus potential changes are likely to occur. In particular, in a high temperature and high humidity environment (e.g., high temperature and high humidity environment of 30° C./85% RH or more), due to the fact that a large amount of moisture is present in the electrophotographic apparatus, potential changes in repeated use for a prolonged period of time (light area potential changes and dark area potential changes) tend to occur.
As a technique of suppressing the potential changes by metal oxide particles, Japanese Patent Laid-Open No. 2012-18370 discloses a technique of using metal oxide particles doped with a different element for a conductive layer.
Japanese Patent Laid-Open No. 2009-288629 discloses a technique of using metal oxide particles for an undercoat layer.
In recent years, an improvement of the durability of an electrophotographic photoconductor and stabilization of an image in repeated use have been demanded with an increase in image quality and an increase in process speed of an electrophotographic apparatus. Therefore, it has been demanded to achieve both suppression of the light area potential changes and suppression of dark area potential changes in repeated use of the electrophotographic photoconductor.
As a result of an examination of the present inventors, it has been found that the following problems arise in the layer configuration of a support medium, an undercoat layer immediately on the support medium, and a photosensitive layer immediately on the undercoat layer. More specifically, it has been found that undercoat layers containing metal oxide particles described in Japanese Patent Laid-Open Nos. 2012-18370 and 2009-288629 have room for an improvement of the light area potential changes and the dark area potential changes in repeated use.